Contemporary flat plate type solar collectors generally include a wooden or metal frame which receives a heat pan having a flat plate with tube means on its top face for fluid to be heated by solar energy, an insulation along the bottom of the plate. The upper edge portion of the frame normally receives a pane of transparent glass, or equivalent material, which is glazed along the frame. Should the glazing develope leaks, water or snow may enter the collector. Unless the collector is suitably vented, pressure variations in the chamber between the glass and the heat pan may be troublesome. Additionally, the portion of the frame above the heat pan reduces the amount of solar energy reaching the pan during early morning and late afternoon hours when the sun is relatively low.
While it is common practice to provide contempory solar collectors with opaque side walls, thus cutting down the solar energy reaching the pan and its tubes during early and late daylight hours, a patent granted in 1913, U.S. Pat. No. 1,068,650, shows a solar water heater including a boiler encased in a generally cylindrical glass cover so that early and late sunlight could heat the boiler. A patent granted in 1940, U.S. Pat. No. 2,213,894, shows a solar collector having a conical tube encased between an insulated base and a transparent, double wall hemispherical cover which is seated in concentric grooves in the base. Neither of the foregoing collectors are of the flat plate type. U.S. Pat. No. 2,907,318, shows a solar collector having transparent side walls and cover, but other features of this collector would retard early and late sunlight from being effective in heating the collector. Another solar collector is shown in U.S. Pat. No. 3,000,375, and has a vacuum chamber which probably has transparent side walls, but this feature is not discussed in the patent. A somewhat dome-shaped, clear plastic cover is shown in U.S. Pat. No. 3,595,216, but is received within encasing flanges of a solar collector and would leave something to be desired in preventing entry of water or snow within the cover. In FIG. 6 of U.S. Pat. No. 3,875,925, a generally dome-shaped transparent cover is provided, but this cover and other portions of the solar collector are inflated by a blower, and weather proofing of the collector appears to be inadequate.
Various display signs use generally dome-shaped transparent covers with an outwardly directed flange along the rim of the dome for securing the cover in place on the remainder of the sign, and are somewhat similar to the cover of the present solar collector.